The present invention relates to a work material holddown and chip removal means for a cutting machine, and more particularly is concerned with a vacuum shroud assembly which removes shreds or chips of cut sheet material and independently holds down the remaining uncut material as a pattern is being cut by the cutting machine.
It is generally known to use an automatically controlled cutting machine to cut a path or a pattern piece from sheet material such as cardboard, plastic, thin metal, acrylic or carbonate. These automatically controlled cutting machines utilize a rotating cutting implement having a plurality of helical cutting edges arranged about an axis of rotation which selectively engage and cut the sheet material when lowered into the material by an actuator and when moved laterally through the material in response to commands generated by a controller. However, in rotating the cutting implement into the sheet material, the helical cutting edges tend to pull the material upwardly thus causing unwanted bending or creasing in the localized area. It is known to utilize a presser foot or holddown to prevent the unwanted deformation of the sheet material along the cutting path. Also known is the use of a presser foot having a vacuum chamber which removes shreds or chips of cut material from the area adjacent the cut path during the cutting operation while simultaneously holding down the remaining uncut sheet material onto the support surface.
However, the presser foot assemblies having vacuum chambers usually are fixed to the cutting implement support structure such that the presser foot is moved vertically with the movements of the cutting implement. Accordingly, contact between the presser foot bottom surface and the upper surface of the sheet material largely depend upon the vertical movement of the cutting implement support structure and the accuracy of the actuator creating the vertical movements. Play or other undesirable variances may develop in these components over a period of time. Subsequently, the play could effect the downward force necessary to create an effective seal between the presser foot bottom surface and the sheet material thus reducing the capacity of the vacuum chamber to evacuate the cut shreds or chips.
Another problem experienced with these assemblies is the impossibility of continually maintaining the same seal between the presser foot bottom surface and the sheet material. During a given cutting operation, the cutting implement and thus the presser foot may be vertically moved several times into and out of engagement with the sheet material. Each time the cutting implement subsequently reengages the sheet material, the presser foot bottom surface must again be reseated. This continual reseating of the presser foot bottom surface is undesirable because a new seal between the presser foot and the sheet material must again be created and, in instances, the effectiveness of each new seal may vary with respect to preceeding or subsequent seals.
Accordingly, it is the object of the present invention to provide a vacuum shroud assembly that is independently fixed to a support on a cutting machine and is capable of being vertically adjustable independently of vertical movement of a cutting apparatus.
It is another object of the present invention to provide a vacuum shroud assembly having a compressible medium formed between the support and the sheet material to provide a constant and even downwardly force on the underside of the presser foot to thereby maintain a seal therebetween.
A further object of the present invention is to provide a vacuum shroud having at least one duct for evacuating air from the shroud to carry away shredded material collected within the vacuum shroud.
Yet still another object of the present invention is to provide a vacuum shroud having an undersurface formed from a low friction material permitting the vacuum shroud to contact the sheet material and slide relative thereto.